1. Field of the Invention
This application relates to covers for water reservoirs.
2. Background of the Related Art
Open-air water reservoirs are frequently used to store drinking water, but pollutants, for example toxic chemicals, animal waste, plants, microorganisms, and even dead animals can easily enter uncovered reservoirs. Covering a reservoir impairs the introduction of pollutants into the reservoir. However, a reservoir cover may be required to maintain a fluid tight cover over hundreds of acres of surface area. For example, a modest size reservoir may have a surface area of 1,000 acres, and a large reservoir may have a surface area that exceeds 25,000 acres.
In addition to covering a large surface area, a reservoir cover must be able to maintain the fluid tight seal over the large area while withstanding powerful seismic events, such as an earthquake, during which panels of the reservoir cover may be displaced from each other independently in all three directional axes. According to the U.S. Geological Survey, each year about 18 major earthquakes occur, which have a magnitude between 7.0 and 7.9, as well as one great earthquake of magnitude 8.0 or greater. Additionally, annually there are dozens of earthquakes between 6.0 and 6.9, and thousands of smaller earthquakes. By way of comparison, an increase of 1.0 in magnitude indicates an increase of 32 times in the energy of an earthquake, and an increase in 10 times in ground displacement. The reservoir cover must be able to withstand these events. Also, the panels of a reservoir cover may be coupled to other panels on every side, thus subjecting the individual panels to forces on every side that are generated by the movement of adjacent panels. Moreover, not only must a reservoir cover withstand the released energy and displacement without collapse, but it must also maintain the fluid tight seal.
Furthermore, since reservoir covers are intended to define a space beneath the cover, the panels of a reservoir cover may be designed with minimal structural support beneath them in order to increase the available space beneath the cover. Finally, a reservoir cover must be water potable to avoid polluting any water in the reservoir. Thus, in a reservoir cover that is made of panels, the panels must be coupled together with connections or joints durable enough to withstand a powerful seismic event that moves the panels independently of each other along three directional axes and displaces the panels to a large magnitude along each axis and withstand forces generated from the movement of surrounding adjacent panels with minimal structural support underneath, while maintaining a water potable cover that is large enough to cover the reservoir with a fluid tight seal.
It is known to provide seals to bridge deck joints, but the seals on bridge deck joints are not potable water approved. Furthermore, bridges have only a fraction of the surface area of a reservoir and may allow runoff of fluids over the side of the bridge. Also, bridge deck joint seals are not designed to withstand independent movement along three axes of direction during a seismic event, nor are bridge deck joint seals designed to withstand the magnitude of potential displacement that may be experienced by the panels of a reservoir cover. Also, bridge sections are often coupled to other sections on only two sides and are thus not exposed to the forces generated by the movement of adjacent sections on all four sides. Finally, bridge deck joints may have more structural support beneath them, for instance along the length of the joint.
Therefore, there is a need for joints that allow panels to be coupled together to form a fluid tight seal over a large surface area while being durable enough to allow the panels to move independently of each other and to a large magnitude of displacement along three directional axes with minimal structural support underneath, while at the same time being water potable.